It is known that certain quinolone compounds possess antibacterial activities. For example, D. Chu, U.S. Pat. No. 4,607,032, has disclosed 1-substituted-amino-2-fluoro-4-oxo-4H-quino[2,3,4-i,j][1,4]benzoxazine-5-c arboxylic acid derivatives which possess antibacterial activity. Closely related quinobenzothiazine and quinobenzoxazine derivatives having antibacterial activity have also been disclosed by Chu in U.S. Pat. Nos. 4,528,285, 4,529,725, and 4,542,133. Certain quinobenzoxazine derivative having antineoplastic activities have been disclosed by Chu in U.S. Pat. No. 5,318,965. It is also known that certain quinolizinone compounds possess antibacterial activities. These compounds, for example, have been disclosed by Chu in PCT application No. WO91/16894, published Nov. 14, 1991.